The nucleotide sequence analysis of mouse mitochondrial DNA is being carried out, using both the Maxam-Gilbert chemical method and the Sanger chain termination method. For the latter purpose, mitochondrial DNA is being subcloned into the filamentous phage cloning vector M13. The position of transfer RNA genes is being located by hybridizing labeled mitochondria tRNA to Southern transfers of mitochondrial DNa restriction digests. The sequencing of these genes will establish the genetic code used by mouse mitochondria. In addition, attempts are underway to obtain translation in E. coli of mitochondrial proteins from cloned DNA.